Some sources claimed that as many as 21 people had been killed in the blast at a mosque in eastern Afghanistan.
A bomb blast inside a mosque in eastern Afghanistan that was being used as a voter registration centre killed at least 13 people and wounded 33, officials said.
Habib Shah Ansari, the provincial head of public health, confirmed the toll from the attack, which took place in the city of Khost, the capital of the province of the same name.
Some reports had placed the death toll as high as 21.
No one immediately claimed responsibility for the attack, but both the Taliban and a local Daesh affiliate reject democratic elections and have targeted them in the past. Daesh is not known to have a presence in Khost, but has expanded its footprint into other areas in recent years.
TRT World's Bilal Sarwary has more.
Last month, a Daesh suicide bomber attacked a voter registration centre in Kabul, killing 60 people and wounding at least 130 others.
Afghanistan plans to hold elections in October, the first since 2014.
The Taliban and Daesh have launched a relentless wave of attacks since the start of the year, killing scores of civilians in the capital, Kabul, and elsewhere. Afghan security forces have struggled to combat the groups since the US and NATO concluded their combat mission at the end of 2014, switching to a counterterrorism and support role.
Elsewhere in Afghanistan, a vehicle carrying shopkeepers on their way to a market struck a roadside bomb in Afghanistan's northern Faryab province, killing seven of them. Police spokesman Karim Yuresh said another civilian was wounded in Sunday's attack, in an area where both the Taliban and Daesh are active.
In the eastern Paktia province, a car bomb killed two people and wounded another three. Abdullah Hsart, the provincial governor's spokesman, said the attack late Saturday targeted Hazart Mohammad Rodwal, a district chief, who was among the wounded. The Taliban claimed responsibility for that attack.